Portable grinder

ABSTRACT

A portable grinder having a vacuum hood enclosing the grinder disc. The hood has a wall of stiff bristles surrounding the periphery of the disc for engaging the surface being ground to permit air to flow through the bristles into the hood and to confine the dust particles inside the hood. The bristles are effectively spring biased to project the bristles forward of the disc to engage the surface before the disc to set up a vacuum in the hood before the grinding begins and after the grinding stops. While the disc is grinding the surface the bristles are biased against the surface to maintain the vacuum. A section of the hood may be removed to enable the disc to reach right up to an intersecting wall or surface.

United States Patent Oimoen 51 July 4, 1972 154] PORTABLE GRINDER 1,914,280 6/1933 Myers ..51/177 T [72] Inventor: Anders Oimoen, East 2008 Third Avenue, a s zzl' Spokane wash. 99202 I [22] Filed: Feb. 12, 1971 FOREIGN PATENTS OR APPLICATIONS [211 App No: 114,816 293,751 12/1953 Switzerland ..51/l70 T Related US, A li ation Dat Primary Examireg-Wifiiag: R. {Armstrong Att ne e s, t. Jo n Ro erts [63] Continuation-impart 6r Ser. N0. 56,553, July 20, or y 1970, abandoned. 57 ABSTRACT 52 US. (:1 ..51/177, 51/273, 5 l/l70T P l grinder having a vacuum 9 enclosing t 51 Int. Cl ..B24b 23/00 grinder e The hood h a of stgff brlsfles Surrounding [58] Field or Search ..51/177, 170 T, 273; 56/3202 the p p 9 t (118C for engaging t w e ground to permit an to flow through the bristles into the hood 56] References Cited and to confine the dust particles inside the hood. The bristles are effectively spring biased to pro ect the bristles forward of UNITED STATES PATENTS the disc to engage the surface before the disc to set up a vacuum in the hood before the grinding begins and after the 2,668,968 2/1954 DObl'OWOlSkl ..5l/177 grinding stops. while the disc is i g the Surface the bris 3'334448 8/1967 Alexande' '51/170 T tles are biased against the surface to maintain the vacuum. A 2,609,555 9/1952 Anderson ..5l/l77 Section of the hood may be removed to enable the disc to i g g l'z 0 reach right up to an intersecting wall or surface. o 3,468,076 9/ l 969 Jones ..51/273 5 Claims, 9 Drawing Figures II II P'ATTENTEDJULE m2 3,573,744

SHEET 2 BF 4 INVENTOR.

ANDEBG O/MOEN w,u.g.amgaowz ATTYO.

PORTABLE GRINDER RELATED PATENT APPLICATION This is a continuation-in-part application of U. S. Pat. application Ser. No. 56,553, filed on July 20, 1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to portable grinders and more particularly to portable grinders having vacuum hoods for preventing the pollution of the surrounding atmosphere.

It is well-known that a large volume of dust particles is generated by portable grinders when used to smooth rough surfaces. Frequently such grinders are utilized for smoothing walls and surfaces of concrete and masonry products. Small particles of the masonary products are generally emitted to the air, presenting a highly polluted atmosphere which is dangerous to the health of the workers in the immediate area. Some operators wear masks to prevent inhalation of the foreign particles. Most masks cause the wearer to perspire leading to discomfort. Consequently, the operators of the portable grinders are only effective for relatively short periods of time. It is well recognized that lung and throat ailments are quite prevalent among such operators. For this reason, many industrial health agencies classify such an occupation as dangerous, enabling workers to be eligible for Workmans Compensation benefits.

It is readily recognized that the mounting of dust collectors or vacuum hoods over the portable grinding wheels or discs is not new for attempting to remove the dust. An example of such a device is disclosed in U. S. Pat. No. 3,468,076 issued Sept. 23, I969. Such a dust collector discloses the use of bristles mounted along the periphery of the collector for engaging the surface being ground. A vacuum conduit is connected to the collector to suck the dust from the grinder. One of the basic problems with this arrangement is the fact that the bristles have to be deformed and deflected substantially before the grinding whee] engages the surface. Such deflection causes voids or channels to occur between the bristles enabling dust particles to flow from the hood outward through the bristles and to cause uneven air flow into the hood. Other examples of similar devices are disclosed in U. S. Pat. Nos: 1,945,03l; 2,527,968; 2,764,852; 2,895,266; 2,929,177 and 3,172,831.

One of the principal purposes of this invention is to provide a portable grinder having facilities for preventing dust and dirt from being emitted into the surrounding atmosphere in a manner that is extremely effective and provides a great deal of versatility.

An additional object of this invention is to provide a portable grinder having a vacuum hood surrounding the abrasive wheel or disc of the grinder that is extremely effective in preventing dust particles from escaping from the hood into the surrounding atmosphere.

A further object of this invention is to provide a portable grinder having facilities for creating a vacuum within the hood before the grinding disc engages the rough surface and maintaining the hood biased against the surface while the grinding disc engages the surface and maintains the hood against the surface after the grinding disc has disengaged from the surface.

An additional object of this invention is to provide a portable grinder having a vacuum hood that is relatively easy to construct, easy to assemble and simple to maintain.

A further object of this invention is to provide a portable grinder having a vacuum hood with several improved features over the hood disclosed in U. S. Pat. No. 3,468,076.

These and other objects and advantages of this invention will become apparent upon reading of the following detailed description of a preferred and alternate embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment and alternate embodiments of this invention are illustrated in the accompanying drawings, in

which:

FIG. 1 is a side view of a portable grinder embodying the principal elements of this invention;

FIG. 2 is a front view of the portable grinder shown in FIG.

FIG. 3 is a vertical cross-section taken along line 3-3 in FIG. 2;

FIG. 4 is a plan view of the portable grinder shown in FIG. 1 illustrating a hood apparatus enclosing a grinding disc;

FIG. 5 is a bottom view of the portable grinder with the grinding disc removed;

FIG. 6 is a plan view of an alternate embodiment of this invention;

FIG. 7 is a fragmentary cross-sectional view taken along line 77 in FIG. 6;

FIG. 8 is a perspective view of an alternate embodiment;

FIG. 9 is a bottom view of an alternate embodiment.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS Now turning to the drawings, there is shown in FIG. 1 and 2 a portable grinder or sander identified in general by.the numeral 10. The portable grinder 10 has a general frame assembly including a motor 12 that is connected to a right angle gear box 13. The right angle gear box 13 has a cylindrical output shaft housing 15 that extends outwardly substantially at right angles to the shaft of the motor 12. An output shaft 17 (FIG. 3) is rotatably mounted in the cylindrical housing 15 and operatively connected to the motor 12 through the right angle drive. The shaft 17 has an end.l8 that protrudes from the housing 15 for receiving a disc assembly 20. The disc assembly 20 includes a mounting hub 21 that is affixed to the shaft end by appropriate means such as screws 22. An abrasive wheel or disc 23 is bolted to the mounting hub 21. The abra sive disc 23 has an abrasive face 24 for engaging the surface to be ground. The disc 23 has an outer periphery 26 of a defined diameter.

The cylindrical shaft housing 15 has an annular outer flange 30 formed thereon. The portable grinder further includes a hood assembly generally designated by the numeral 32 which comprises a spool 33 that is affixed to the outside of the housing 15 eoaxially with the shaft 17. The spool is fixed on the outside of the housing I3 with an annular flange 34 engaging the flange 30. The spool 33 further includes an annular flange 35 spaced from the annular flange 34.

Spool 33 may be fabricated by brazing one of the flanges 34, 35 after mounting of enclosure 36 as discussed below.

In one embodiment, the hood assembly 32 includes a dishshaped enclosure or hood 36 that is mounted eoaxially on the housing 15. The enclosure 36 has a circular shaped radial body 37 with a central aperture 38 formed therein. The aperture 38 has a diameter less than the outer diameter of the annular flanges 34 and 35. The enclosure 36 is mounted coaxially about the spool 33 and is capable of sliding on the spool 33 between the annular flanges 34 and 35 in an axial direction to the shaft 17.

The enclosure 36 includes an annular skirt or flange 40 that extends downwardly encircling the abrasive disc 23. The diameter of the skirt or flange 40 is slightly greater than that of the abrasive disc so that the skirt is spaced a small distance from the periphery 26.

An air-pervious shield 41 is mounted to the skirt 40 for engaging the surface to be ground, encircling the disc to permit air to flow into the hood and to restrict the movement of the dust from the hood. The shield 41 is formed by arcuate bristles sections 43 that are attached to the skirt 40 around the entire skirt. The bristle segments are formed of stiff bristles 44 that are capable of being slightly deflected as the grinder is moved over the rough surfaces while being sufficiently stiff to support the portable grinder. Air-pervious felt material has also been found to serve satisfactory as the shield material. The bristle segments 43 are attached to the skirt 40 by screws 46.

The hood assembly 32 also includes air outlet conduits 48 and 50 that are formed in the body 37 that extends outward 'at inclined angles for receiving flexible vacuum hoses 51. The flexible vacuum hoses are connected to a vacuum source for applying a pressure differential across the shield 41 to cause the air to flow through the shield 41 and draw the dust from the hood out through the flexible vacuum hoses 51.

One of the important features of this embodiment is the provision of a spring means operatively connected between the portable grinding housing and the shield 41 to project the shield 41 forward of the disc face 24 so that when the portable grinder is applied to the surface to be ground the shield initially engages the surface to create a vacuum in the hood before the abrasive disc engages the surface and generates the dust. As the grinder is pushed against the surface, the spring means allows the shield 41 to move rearward with respect to the disc. The spring means further maintains a positive pressure on the shield 41 to press the shield 41 against the surface at all times to minimize the possibility of dust flowing out from the periphery of the hood. The spring means also maintains the shield in contact with the surfaces during initial release of the portable grinder so that any residual dust remaining in the hood or between the disc and the surface is withdrawn through the flexible hoses. The spring means also allows the operator to slightly tilt the grinder to engage the surface with only a sector of the disc while maintaining the shield in contact with the surface about the entire periphery of the hood. Stated another way, the spring allows the hood to tilt, with respect to the rotational axis of the disc to maintain the shield in contact with the surface when the grinder is tilted to contact the surface with only a portion of the disc face.

The spring means is provided through the use of a compression spring 53 mounted between the annular flange 34 and the hood body 37 immediately surrounding the central aperture 38 as shown in FIG. 3.

It can be said that the hood 32 is slidably mounted on the housing 15 for axial movement between an extended position in which the shield 4I extends forward of the face of the disc 23 and a retracted position in which the shield is flush or in the same plane as the disc face 24 as shown in FIG. 3. A further advantage of this feature is the ability to maintain the shield 41 in engagement with the surface at all times even though the stiff bristles or felt may become worn. The bristles or felt need not be replaced when it becomes only partly worn.

Another important feature enables the portable grinder to Y be utilized for grinding surfaces right up to intersecting wall or floor surfaces. The body 34 includes a removable body sector 55 that encloses an angular segment of the abrasive disc as shown in FIG. 4. The body sector 55 is removable to expose the periphery of the disc between points 57 and 58 as shown in FIG. 5. When the body sector 55 is removed the portable grinder may be moved so that the abrasive disc is capable of grinding the surface right up to the intersecting walls or corner sections. When the body section 55 is removed, an opening 60 (FIG. is formed.

Parallel elongated slots 61 are formed in the body 37 to slidably receive an air baffle 62 (FIGS. 3 and 5) that projects into the opening 60 to restrict and limit the amount of air flowing into the hood through the opening 60. If it were not for the baffle 62, sufficient air would flow through the opening 60 to reduce the vacuum pressure to zero and greatly limit the effectiveness of the portable grinder. The baffle 62 projects into the opening to provide a small opening or small space between the baffle and the grinding disc so that sufficient vacuum pressure is maintained within the hood to cause air to flow into the hood about the entire periphery of the hood to prevent dust from leaving the hood.

In an alternate embodiment shown in FIGS. 6 and 7 there is shown a portable grinder with a hood assembly having a body 65 similar to body 37 except having a curved groove 66 formed therein that creates a raised annular rib that extends arcuately about the aperture 38. The arcuate groove 66 extends from point 67 in an arcuate manner about the central aperture 38 to an outlet conduit 69. The cross-section of the groove progressively increases in the same direction as the rotation of the disc.

The body 65 has a side opening 70 with parallel side walls 71 that extend outward substantially tangent to the remainder of the periphery. A side hood element 72 is slidably mounted on the body 65 over the side opening. The hood element 72 has a top edge 73 and side edges 74. An air-impervious shield 75 is mounted about the edges 73 and 74 for engaging the intersecting wall to prevent dust from flowing out the side opening 70. The side hood element is spring-biased outward from the center aperture 38 to engage the intersecting wall before the periphery of the disc 24. Specifically, a spring 76 extends around the sleeve 33 with ends crossing and extending outward to the top edge 73 where they are affixed. The spring 76 maintains the shield 75 firmly against the intersecting wall.

In the embodiment illustrated in FIG. 8, a hood 85 is shown in perspective having a top surface 86 with a central aperture therein to receive a sleeve 88 that is connectable to the flange of the grinder. An air outlet 90 is formed in the top surface for connecting to a source of vacuum. The hood 85 has a skirt 91 extending downward from the periphery of the top surface 86. The hood has a spring means 92 .operatively connected between the grinder and the shield for biasing the shield against the surface to be ground in a manner previously described. The spring means 92 includes wire springs 93 and 94 affixed at attachment points 95 and 96 respectively to the sleeve 88. Each of the springs 93 and 94 have free ends 98 and v 100 that extend downwardly engaging the top surface 86 at various locations to normally bias the hood 85 to a coaxial normally perpendicular orientation to rotational axis of the ground.

An additional embodiment is illustrated in FIG. 9 showing a bottom view of a hood 102. The hood I02 has a bottom surface 103 with a central aperture for receiving a sleeve I07 therein. An air outlet I05 is provided in the hood for connection to the vacuum source. The hood 102 has a spring means for enabling the hood to move both axially and in a tilt direction to the rotational axis of the grinder. The spring means includes springs I11 and 112 that are attached to the bottom surface 103 at attachment points 118 and 120. The spring 111 has ends 113 and 114 that extend inward from the bottom surface to connect with the sleeve 107. Likewise, the spring 112 has free ends 115 and 116 that extend radially inwardconnecting with the sleeve 107. The ends 113 to 116 connect with the sleeve at various angular positions to provide a uniform spring bias between the grinder and the shield to maintain the shield in contact with the surface in the manner previously described.

It should be understood that the above described embodiments are simply illustrative of the principles of the invention and that numerous other embodiments may be readily devised by those skilled in the art without deviating from the principles thereof. Therefore, only the following claims are intended to define this invention.

What is claimed is:

1. In combination with a portable grinder having:

a shaft housing;

a shaft rotatably mounted in the shaft housing with one end protruding therefrom;

an annular abrasive element mounted on the protruding end having a periphery and an abrasive face;

a motor operatively connected to the disc shaft for rotating the shaft and element to grind a surface with the abrasive face and thereby generate dust particles;

an improvement of a vacuum hood assembly, comprising:

an adapter sleeve mounted to the shaft housing coaxially surrounding the shaft;

a dust hood mounted on the sleeve substantially enclosing the abrasive element except for the face;

said dust hood having a periphery with a substantially circular air pervious shield composed of stiff bristles encircling and radially spaced from the periphery of the disc for engaging the surface to permit air to flow into the hood through the bristles about the periphery of the abrasive element and confine the dust particles within the hood; said dust hood being slidably mounted on the sleeve for axial movement relative to the shaft between an extended position in which the bristles extend forward of the abrasive face and a retracted position in which the bristles terminate substantially flush with the disc face; spring means mounted on the sleeve resiliently biasing the dust hood toward the extended position for (1) biasing the bristles into contact with the surface before the abrasive face as the grinder is applied to the surface, (2) maintaining a positive pressure of the bristles against the surface during engagement by the abrasive face, and (3) maintaining the bristles in contact with the surface while the abrasive face is being initially withdrawn from the surface; and

an air duct formed in said hood and being adapted to operatively connect an air vacuum source to create a vacuum in the hood and draw air through the bristles, into the hood and out through the air duct to carry dust particles therewith.

2. The combination as defined in claim 1 wherein the hood has a peripheral sector that is removable to expose a peripheral segment of the abrasive element to enable the element to grind the surface until the periphery of the element engages an intersecting surface.

3. The combination as defined in claim 1 wherein the hood has a curved, tapered groove formed therein that extends arcuately about the shaft housing and progressively increases in cross-section in the direction of rotation of the disc terminating at an air duct.

4. The combination as defined in claim 2 wherein the hood has an air baffle mounted therein adjacent the removable sector to limit the amount of air drawn through a hood opening defined by the removal of the sector to maintain a vacuum within the hood even though the sector is removed.

5. The combination as defined in claim 1 wherein the spring means is adapted to maintain the shield in engagement with the surface even though the grinder is tilted slightly to grind the surface with only a portion of the abrasive face. 

1. In combination with a portable grinder having: a shaft housing; a shaft rotatably mounted in the shaft housing with one end protruding therefrom; an annular abrasive element mounted on the protruding end having a periphery and an abrasive face; a motor operatively connected to the disc shaft for rotating the shaft and element to grind a surface with the abrasive face and thereby generate dust particles; an improvement of a vacuum hood assembly, comprising: an adapter sleeve mounted to the shaft housing coaxially surrounding the shaft; a dust hood mounted on the sleeve substantially enclosing the abrasive element except for the face; said dust hood having a periphery with a substantially circular air pervious shield composed of stiff bristles encircling and radially spaced from the periphery of the disc for engaging the surface to permit air to flow into the hood through the bristles about the periphery of the abrasive element and confine the dust particles within the hood; said dust hood being slidably mounted on the sleeve for axial movement relative to the shaft between an extended position in which the bristles extend forward of the abrasive face and a retracted position in which the bristles terminate substantially flush with the disc face; spring means mounted on the sleeve resiliently biasing the dust hood toward the extended position for (1) biasing the bristles into contact with the surface before the abrasive face as the grinder is applied to the surface, (2) maintaining a positive pressure of the bristles against the surface during engagement by the abrasive face, and (3) maintaining the bristles in contact with the surface while the abrasive face is being initially withdrawn from the surface; and an air duct formed in said hood and being adapted to operatively connect an air vacuum source to create a vacuum in the hood and draw air through the bristles, into the hood and out through the air duct to carry dust particles therewith.
 2. The combination as defined in claim 1 wherein the hood has a peripheral sector that is removable to expose a peripheral segment of the abrasive element to enable the element to grind the surface until the periphery of the element engages an intersecting surface.
 3. The combination as defined in claim 1 wherein the hood has a curved, tapered groove formed therein that extends arcuately about the shaft housing and progressively increases in cross-section in the direction of rotation of the disc terminating at an air duct.
 4. The combination as defined in claim 2 wherein the hood has an air baffle mounted therein adjacent the removable sector to limit the amount of air drawn through a hood opening defined by the Removal of the sector to maintain a vacuum within the hood even though the sector is removed.
 5. The combination as defined in claim 1 wherein the spring means is adapted to maintain the shield in engagement with the surface even though the grinder is tilted slightly to grind the surface with only a portion of the abrasive face. 